This invention relates to a fuel controller for an internal combustion engine. More particularly, it relates to a fuel controller which can stop the supply of fuel to an individual cylinder which is misfiring.
Electronic fuel injection systems are becoming increasingly common in internal combustion engines for automobiles. In these systems, an optimal air-fuel ratio is calculated on the basis of various operating parameters such as the engine speed, the air intake rate, the air intake temperature, and the engine temperature. Electromagnetically-operated fuel injectors are then controlled so as to achieve an air-fuel mixture having the optimal air-fuel ratio.
Many cars are equipped with a catalytic converter for removing harmful components from the engine exhaust gases. A typical catalytic converter is a three-way catalytic converter which simultaneously oxidizes carbon monoxide and hydrocarbons while it reduces oxides of nitrogen (NOx). An electronic fuel injection system is usually designed to maintain the air-fuel ratio near the stoichiometric ratio so that the catalytic converter can function effectively.
Occasionally, due to breakage of parts, poor electrical connections, or equipment malfunctions, combustion does not take place properly in the cylinders of an engine and so-called "misfiring" occurs. Due to misfiring, a mixture of uncombusted fuel and air flows into the catalytic converter, and a sudden chemical reaction takes place, causing an enormous increase in the temperature of the catalytic converter. Under these conditions, the catalytic converter can not function properly, and harmful exhaust gases are discharged into the atmosphere. The increase in temperature also produces degradation of the catalytic converter and shortens its life span. Furthermore, when the automobile is stationary, if dead grass or other combustible material should contact the catalytic converter when it is at an abnormally high temperature due to misfiring, there is the possibility of a fire starting.